Synthesis of 2′,3′-Modified Carbocyclic L-Nucleoside Analogues

Asymmetric total synthesis of prostaglandin C2 TBS ether

We disclose an asymmetric total synthesis of prostaglandin C₂ TBS ether, a derivative of an extremely sensitive natural prostaglandin C₂. The key to the synthesis is a SmI₂-mediated ketyl-enoate reaction that leads to the formation of the functionalized cyclopentane ring with high-level stereochemical control. Access to the crucial alkene system is realized late in the synthesis by the implementation of a Grignard addition/dehydration/metathesis sequence.

Advances in Therapeutic L-Nucleosides and L-Nucleic Acids with Unusual Handedness

Nucleic-acid-based small molecule and oligonucleotide therapies are attractive topics due to their potential for effective target of disease-related modules and specific control of disease gene expression. As the non-naturally occurring biomolecules, modified DNA/RNA nucleoside and oligonucleotide analogues composed of L-(deoxy)riboses, have been designed and applied as innovative therapeutics with superior plasma stability, weakened cytotoxicity, and inexistent immunogenicity. Although all the chiral centers in the backbone are mirror converted from the natural D-nucleic acids, L-nucleic acids are equipped with the same nucleobases (A, G, C and U or T), which are critical to maintain the programmability and form adaptable tertiary structures for target binding. The types of L-nucleic acid drugs are increasingly varied, from chemically modified nucleoside analogues that interact with pathogenic polymerases to nanoparticles containing hundreds of repeating L-nucleotides that circulate durably in vivo. This article mainly reviews three different aspects of L-nucleic acid therapies, including pharmacological L-nucleosides, Spiegelmers as specific target-binding aptamers, and L-nanostructures as effective drug-delivery devices.

Diastereoselective Flexible Synthesis of Carbocyclic C-Nucleosides

Carbocyclic C-nucleosides are quite rare. Our route enables flexible preparation of three classes of these nucleoside analogs from common precursors-properly substituted cyclopentanones, which can be prepared racemic (in six steps) or optically pure (in ten steps) from inexpensive norbornadiene. The methodology allows flexible manipulation of individual positions around the cyclopentane ring, namely highly diastereoselective installation of carbo- and heterocyclic substituents at position 1', orthogonal functionalization of position 5', and efficient inversion of stereochemistry at position 2'. Newly prepared carbocyclic C-analog of tubercidine, profiled in MCF7 (breast cancer) and HFF1 (human foreskin fibroblasts) cell cultures, is less potent than tubercidine itself, but more selectively toxic toward the tumorigenic cells.

Synthesis and biological evaluation of phosphoramidate prodrugs of two analogues of 2-deoxy-d-ribose-1-phosphate directed to the discovery of two carbasugars as new potential anti-HIV leads

2-Deoxy-α-d-ribose-1-phosphate is of great interest as it is involved in the biosynthesis and/or catabolic degradation of several nucleoside analogues of biological and therapeutic relevance. However due to the lack of a stabilising group at its 2-position, it is difficult to synthesize stable prodrugs of this compound. In order to overcome this lack of stability, the synthesis of carbasugar analogues of 2-deoxyribose-1-phosphate was envisioned. Herein the preparation of a series of prodrugs of two carbocyclic analogues of 2-deoxyribose-1-phosphate using the phosphoramidate ProTide technology, along with their biological evaluation against HIV and cancer cell proliferation, is reported.